The present invention relates to an ophthalmic laser apparatus, and more particularly to an ophthalmic laser apparatus suitable to a probe for transscleral retina photocoagulation.
A photocoagulation method in which a treatment light is directed to an ocular through an cornea from a lens system, and another photocoagulation method in which a treatment light is directed to an endprobe inserted into an eye through a light cable and the directed light is irradiated to an ocular, have been known as methods for photocoagulating the ocular of the eye to be treated. A treatment method in which a probe is inserted externally of the eye to be treated and the retina is photocoagulated by a YAG laser through the sclera, has also been known. Those treatment methods are selectively used depending on a position of the coagulation.
Since such an apparatus is expensive, it is usually not a stand-alone apparatus but it is shared with an apparatus for coagulating other than the ocular such as a ciliary body, and it is selectively used.
A cryocoagulation method in which a probe is inserted externally of the eye to be treated and the retina is coagulated through the sclera has also been known.
When the probe is to be inserted externally of the eye to be treated to photocoagulate the retina through the sclera, it is necessary to press the sclera in order to locate an affected part. Where a probe of a conventional shape is used, a tip end thereof is likely to damage the sclera.
Further, because the apparatus is not constructed as a stand-alone unit it is necessary to direct lights to a slit lamp, through a delivery optical system such as a binocular indirect ophthalmoscope, and various probes. As a result, there is a restriction in an incident angle to an optical fiber in the light cable for the probe and a divergence angle of a light beam at the end of the probe is not always optimum. When a semiconductor laser is used, the coagulation area per irradiation is 1/3 to 1/6 of the coagulation area attained by the cryocoagulation method and hence the number of times of irradiation increases.
There is a limit in controlling the spread angle in the laser apparatus.